Ethereum is a platform for decentralized and truthful applications that run on a global, peer-to-peer network without any administrators or a single point of failure. These applications have zero downtime and anyone can create them: it is permissionless innovation. The applications are truthful, immutable and always interoperate as they are coded. From this perspective, the terminology of smart contracts is reasonable in that they are the ultimate in contracts that always follow the terms set at their creation.

The core of what makes this possible is effectively a World Computer. Technically called the Ethereum Virtual Machine (EVM), it includes operations for computation and data storage. A transaction represents a single session within the World Computer. It is the unit of interaction, similar to how a sentence is the unit of grammatical meaning, even though a single sentence can contain many words.

What is Gas?

Gas is the metering unit for use of the World Computer. As an analogy, electricity is metered by kilowatt hours. Using more computation and storage in Ethereum means that more gas is used. One fundamental reason for metering is that it provides an incentive for people (miners) to operate the World Computer. These miners get a fee for processing transactions, which is determined by the metering scheme: gas.

Each operation in the EVM consumes gas. For example, a multiplication (MUL) consumes 5 gas and an addition (ADD) consumes 3 gas.